Why did this year of training fail to restore cardiac compliance? New evidence suggests that the structural plasticity of myocardial cells in the elderly may be functionally constrained by the accumulation of toxic metabolites called advanced glycation end-products (AGEs). AGEs are arrays of protein which have been non-enzymatically cross-linked by sugars; these arrays increase the stiffness of arterial walls and the myocardium. Investigators have recently developed a drug capable of cleaving AGE cross-links. Termed ALT-711, this drug has been shown to be safe in human studies with varying degrees of efficacy on endpoints such as blood pressure and non-invasive indices of diastolic function. Based on animal studies, we hypothesize that AGE cross-links must be broken before a meaningful improvement in cardiac compliance can occur with exercise training in sedentary seniors.